/*
   * Broadcom UniMAC MDIO bus controller driver
   *
   * Copyright (C) 2014, Broadcom Corporation
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   */
  
  #include <linux/kernel.h>
  #include <linux/phy.h>
  #include <linux/platform_device.h>
  #include <linux/sched.h>
  #include <linux/module.h>
  #include <linux/io.h>
  #include <linux/delay.h>
  
  #include <linux/of.h>
  #include <linux/of_platform.h>
  #include <linux/of_mdio.h>
  
  #define MDIO_CMD		0x00
  #define  MDIO_START_BUSY	(1 << 29)
  #define  MDIO_READ_FAIL		(1 << 28)
  #define  MDIO_RD		(2 << 26)
  #define  MDIO_WR		(1 << 26)
  #define  MDIO_PMD_SHIFT		21
  #define  MDIO_PMD_MASK		0x1F
  #define  MDIO_REG_SHIFT		16
  #define  MDIO_REG_MASK		0x1F
  
  #define MDIO_CFG		0x04
  #define  MDIO_C22		(1 << 0)
  #define  MDIO_C45		0
  #define  MDIO_CLK_DIV_SHIFT	4
  #define  MDIO_CLK_DIV_MASK	0x3F
  #define  MDIO_SUPP_PREAMBLE	(1 << 12)
  
  struct unimac_mdio_priv {
  	struct mii_bus		*mii_bus;
  	void __iomem		*base;
  };
  
  static inline void unimac_mdio_start(struct unimac_mdio_priv *priv)
  {
  	u32 reg;
  
  	reg = __raw_readl(priv->base + MDIO_CMD);
  	reg |= MDIO_START_BUSY;
  	__raw_writel(reg, priv->base + MDIO_CMD);
  }
  
  static inline unsigned int unimac_mdio_busy(struct unimac_mdio_priv *priv)
  {
  	return __raw_readl(priv->base + MDIO_CMD) & MDIO_START_BUSY;
  }
  
  static int unimac_mdio_read(struct mii_bus *bus, int phy_id, int reg)
  {
  	struct unimac_mdio_priv *priv = bus->priv;
  	unsigned int timeout = 1000;
  	u32 cmd;
  
  	/* Prepare the read operation */
  	cmd = MDIO_RD | (phy_id << MDIO_PMD_SHIFT) | (reg << MDIO_REG_SHIFT);
  	__raw_writel(cmd, priv->base + MDIO_CMD);
  
  	/* Start MDIO transaction */
  	unimac_mdio_start(priv);
  
  	do {
  		if (!unimac_mdio_busy(priv))
  			break;
  
  		usleep_range(1000, 2000);
  	} while (timeout--);
  
  	if (!timeout)
  		return -ETIMEDOUT;
  
  	cmd = __raw_readl(priv->base + MDIO_CMD);
  
  	/* Some broken devices are known not to release the line during
  	 * turn-around, e.g: Broadcom BCM53125 external switches, so check for
  	 * that condition here and ignore the MDIO controller read failure
  	 * indication.
  	 */
  	if (!(bus->phy_ignore_ta_mask & 1 << phy_id) && (cmd & MDIO_READ_FAIL))
  		return -EIO;
  
  	return cmd & 0xffff;
  }
  
  static int unimac_mdio_write(struct mii_bus *bus, int phy_id,
  			     int reg, u16 val)
  {
  	struct unimac_mdio_priv *priv = bus->priv;
  	unsigned int timeout = 1000;
  	u32 cmd;
  
  	/* Prepare the write operation */
  	cmd = MDIO_WR | (phy_id << MDIO_PMD_SHIFT) |
  		(reg << MDIO_REG_SHIFT) | (0xffff & val);
  	__raw_writel(cmd, priv->base + MDIO_CMD);
  
  	unimac_mdio_start(priv);
  
  	do {
  		if (!unimac_mdio_busy(priv))
  			break;
  
  		usleep_range(1000, 2000);
  	} while (timeout--);
  
  	if (!timeout)
  		return -ETIMEDOUT;
  
  	return 0;
  }
  
  /* Workaround for integrated BCM7xxx Gigabit PHYs which have a problem with
   * their internal MDIO management controller making them fail to successfully
   * be read from or written to for the first transaction.  We insert a dummy
   * BMSR read here to make sure that phy_get_device() and get_phy_id() can
   * correctly read the PHY MII_PHYSID1/2 registers and successfully register a
   * PHY device for this peripheral.
   *
   * Once the PHY driver is registered, we can workaround subsequent reads from
   * there (e.g: during system-wide power management).
   *
   * bus->reset is invoked before mdiobus_scan during mdiobus_register and is
   * therefore the right location to stick that workaround. Since we do not want
   * to read from non-existing PHYs, we either use bus->phy_mask or do a manual
   * Device Tree scan to limit the search area.
   */
  static int unimac_mdio_reset(struct mii_bus *bus)
  {
  	struct device_node *np = bus->dev.of_node;
  	struct device_node *child;
  	u32 read_mask = 0;
  	int addr;
  
  	if (!np) {
  		read_mask = ~bus->phy_mask;
  	} else {
  		for_each_available_child_of_node(np, child) {
  			addr = of_mdio_parse_addr(&bus->dev, child);
  			if (addr < 0)
  				continue;
  
  			read_mask |= 1 << addr;
  		}
  	}
  
  	for (addr = 0; addr < PHY_MAX_ADDR; addr++) {
  		if (read_mask & 1 << addr)
  			mdiobus_read(bus, addr, MII_BMSR);
  	}
  
  	return 0;
  }
  
  static int unimac_mdio_probe(struct platform_device *pdev)
  {
  	struct unimac_mdio_priv *priv;
  	struct device_node *np;
  	struct mii_bus *bus;
  	struct resource *r;
  	int ret;
  
  	np = pdev->dev.of_node;
  
  	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
  	if (!priv)
  		return -ENOMEM;
  
  	r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
  
  	/* Just ioremap, as this MDIO block is usually integrated into an
  	 * Ethernet MAC controller register range
  	 */
  	priv->base = devm_ioremap(&pdev->dev, r->start, resource_size(r));
  	if (!priv->base) {
  		dev_err(&pdev->dev, "failed to remap register
  ");
  		return -ENOMEM;
  	}
  
  	priv->mii_bus = mdiobus_alloc();
  	if (!priv->mii_bus)
  		return -ENOMEM;
  
  	bus = priv->mii_bus;
  	bus->priv = priv;
  	bus->name = "unimac MII bus";
  	bus->parent = &pdev->dev;
  	bus->read = unimac_mdio_read;
  	bus->write = unimac_mdio_write;
  	bus->reset = unimac_mdio_reset;
  	snprintf(bus->id, MII_BUS_ID_SIZE, "%s", pdev->name);
  
  	bus->irq = kcalloc(PHY_MAX_ADDR, sizeof(int), GFP_KERNEL);
  	if (!bus->irq) {
  		ret = -ENOMEM;
  		goto out_mdio_free;
  	}
  
  	ret = of_mdiobus_register(bus, np);
  	if (ret) {
  		dev_err(&pdev->dev, "MDIO bus registration failed
  ");
  		goto out_mdio_irq;
  	}
  
  	platform_set_drvdata(pdev, priv);
  
  	dev_info(&pdev->dev, "Broadcom UniMAC MDIO bus at 0x%p
  ", priv->base);
  
  	return 0;
  
  out_mdio_irq:
  	kfree(bus->irq);
  out_mdio_free:
  	mdiobus_free(bus);
  	return ret;
  }
  
  static int unimac_mdio_remove(struct platform_device *pdev)
  {
  	struct unimac_mdio_priv *priv = platform_get_drvdata(pdev);
  
  	mdiobus_unregister(priv->mii_bus);
  	kfree(priv->mii_bus->irq);
  	mdiobus_free(priv->mii_bus);
  
  	return 0;
  }
  
  static const struct of_device_id unimac_mdio_ids[] = {
  	{ .compatible = "brcm,genet-mdio-v4", },
  	{ .compatible = "brcm,genet-mdio-v3", },
  	{ .compatible = "brcm,genet-mdio-v2", },
  	{ .compatible = "brcm,genet-mdio-v1", },
  	{ .compatible = "brcm,unimac-mdio", },
  	{ /* sentinel */ },
  };
  MODULE_DEVICE_TABLE(of, unimac_mdio_ids);
  
  static struct platform_driver unimac_mdio_driver = {
  	.driver = {
  		.name = "unimac-mdio",
  		.of_match_table = unimac_mdio_ids,
  	},
  	.probe	= unimac_mdio_probe,
  	.remove	= unimac_mdio_remove,
  };
  module_platform_driver(unimac_mdio_driver);
  
  MODULE_AUTHOR("Broadcom Corporation");
  MODULE_DESCRIPTION("Broadcom UniMAC MDIO bus controller");
  MODULE_LICENSE("GPL");
  MODULE_ALIAS("platform:unimac-mdio");